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13.  英国《自然》杂志报道,科学家最近研制成了以锶原子做钟摆的“光格钟”,成了世界上最精确的钟。已知一种锶原子的相对原子质量为88,其质子数是38,则一个这种锶原子中含有的微粒总数为 (   )

A.38            B.50             C.88            D.126

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12.  下列各反应中,各物质之间的质量比为1∶1∶2的是······································· (   )

A.H2 +Cl22HCl              B.N2 +O22NO

C.S + O2SO2              D.Fe + S FeS

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11.  下列化学方程式书写完全正确的是··································································· (   )

A.2H2O = 2H2 + O2                                    B.Mg + O2MgO2

C.4Fe + 3O22Fe2O3              D.CO2 + Ca(OH)2 = CaCO3↓+ H2O

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10.  某纯净物在受热时发生分解反应生成水、二氧化碳和氨气(NH3)三种物质。下列对该物质的推断中,错误的是······················································································································· (   )

A.该物质一定是化合物   

B.该物质是由氢、氧、氮、碳四种元素组成的

C.该物质是由水分子、二氧化碳分子、氨分子构成的

D.该物质中氮、氢、碳、氧元素的质量比可能是14∶5∶12∶48

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9. 金属元素M只有一种化合价,其氧化物的化学式为MO,则下列化学式中错误的是(   )

A.MCl2          B.MCO3         C.MSO4          D. MOH

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8. 已知,若有m个水分子生成,则参加反应的氧原子的个数为··························· (   )

A.m/2           B.m            C.3m/2           D.2m

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7. 下列有关实验现象的描述正确的是··································································· (   )

A.碳在氧气中燃烧,生成白烟               

B.铁丝在空气中燃烧,发出耀眼的强光,生成黑色固体          

C.硫在空气中燃烧,生成一种有刺激性气味的气体         

D.红磷在空气中燃烧,生成五氧化二磷

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6. 我国的淡水资源非常匮乏,同学们在生活中要注意节约用水,保护水资源。下列是某附属中学初三(1)班的郑灿同学周日一天的用水情况,其中我们应该提倡的是················································· (   )

①早上间歇用水刷牙                ②中午淘米淘菜的水浇花 

③吃饭后不间断用水洗碗              ④下午洗衣服的水用来冲厕所 

⑤晚上洗澡打香皂时让水龙头继续流水

A.①②④        B.②③⑤       C.③④⑤         D.②④⑤

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5. 自然界中发生的下列现象不是由于空气污染造成的是······································· (   )

A.酸雨危害       B.海洋赤潮        C.光化学烟雾      D.臭氧层空洞

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4. 空气中氧气和氮气的体积比约为······································································ (   )

A.1︰1           B.1︰5           C.1︰4           D.1︰2

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